Initial Heavy Metal Concentration Research Articles

Integrated Electro-Ozonation and Fixed-Bed Column for the Simultaneous Removal of Emerging Contaminants and Heavy Metals from Aqueous Solutions

In the current study, an integrated physiochemical method was utilized to remove tonalide (TND) and dimethyl phthalate (DMP) (as emerging contaminants, ECs), and nickel (Ni) and lead (Pb) (as heavy metals), from synthetic wastewater. In the first step of the study, pH, current (mA/cm2), and voltage (V) were set to 7.0, 30, and 9, respectively; then the removal of TND, DMP, Ni, and Pb with an electro-ozonation reactor was optimized using response surface methodology (RSM). At the optimum reaction time (58.1 min), ozone dosage (9.4 mg L−1), initial concentration of ECs (0.98 mg L−1), and initial concentration of heavy metals (28.9 mg L−1), the percentages of TND, DMP, Ni, and Pb removal were 77.0%, 84.5%, 59.2%, and 58.2%, respectively. For the electro-ozonation reactor, the ozone consumption (OC) ranged from 1.1 kg to 3.9 kg (kg O3/kg Ecs), and the specific energy consumption (SEC) was 6.95 (kWh kg−1). After treatment with the optimum electro-ozonation parameters, the synthetic wastewater was transferred to a fixed-bed column, which was filled with a new composite adsorbent (named BBCEC), as the second step of the study. BBCEC improved the efficacy of the removal of TND, DMP, Ni, and Pb to more than 92%.

Bioremediation of heavy metals from the aqueous environment using Artocarpus heterophyllus (jackfruit) seed as a novel biosorbent

Biosorption is an environment-friendly and economic technique to remediate heavy metals from aqueous systems. In the present study, Artocarpus heterophyllus seed powder was used as a biosorbent material to remove different heavy metals. The batch adsorption studies confirmed the higher removal percentage of the Artocarpus heterophyllus (jackfruit) seed powder for arsenic (As5+), cadmium (Cd2+), and chromium (Cr6+) while lower efficiency was observed for other heavy metals like copper (Cu2+), zinc (Zn2+) and nickel (Ni2+). Optimization of different process parameters was carried out and the optimum conditions were: adsorbent weight of 0.5 g for the initial concentration of heavy metals as 40 μg/L, 30 mg/L, and 30 mg/L; contact time of 10 h, 8 h, and 6 h; process temperature from 25 to 30 °C; pH of 7, 7.5, and 7.5 for As5+, Cd2+, and Cr6+ respectively. The SEM-EDX, FTIR, and XRD studies before and after adsorption of heavy metals resulted in affirmative observations. The equilibrium data of the study was well fitted for Langmuir isotherm for As5+, Cd2+, and Cr6+, Freundlich for As5+and Cr6+, Dubinin-Radushkevich for Cd2+and Cr6+. The kinetic and thermodynamic study confirmed that the adsorption of all three heavy metals was following the pseudo-second-order kinetics with the endothermic and spontaneous process respectively. The cost analysis of the process confirmed that the whole process was cost-effective compared to other processes. Hence the Artocarpus heterophyllus seed powder was verified for its high heavy metal remediation efficiency from aqueous environments along with the added advantages of being eco-friendly and economic compared to other alternatives.

Biosorption optimization of lead(II) and cadmium(II) ions by two novel nanosilica-immobilized fungal mutants.

This study aims at immobilization of fungal mutants on nanosilica (NSi)-carriers for designing efficient biosorbents as a significant new technology for decontamination practices and maximizing their heavy metal (HM) sorption proficiency through the experimental design methodology. Endophytic fungal mutant strains, Chaetomium globosum El26 mutant and Alternaria alternata S5 mutant were heat inactivated and then immobilized, each separately, on NSi carriers to formulate two separated nano-biosorbents. The formulated NSi-Chaetomium globosum El26 mutant (NSi-Chae El26 m) was investigated for Pb+2 uptake while, the formulated NSi-Alternaria alternata S5 mutant (NSi-Alt S5 m) was investigated for Cd+2 uptake, each through a batch equilibrium protocol. Before and after the metal sorption process, the designed nano-biosorbents were characterized via scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared analysis. Sorption pH, contact time, sorbent concentration, and initial HM concentration were statistically optimized using a Box-Behnken design. Results showed that NSi-Chae El26 m was efficient in Pb+2 uptake with maximum biosorption capacities of 199.0, while NSi-Alt S5 m was efficient in Cd+2 uptake with maximum biosorption capacities of 162.0mg g-1 . Moreover, the equilibrium data indicated that the adsorption of Pb+2 and Cd+2 by the tested nano-biosorbents fitted to the Freundlich isotherm. The formulated nano-biosorbents resulted in higher HM biosorption of metal ions from aqueous solution than that obtained by the free fungal biomass. The biosorption statistical modelling described the interactions between the tested sorption parameters and predicted the optimum values for maximum HM biosorption capacity by the two designed nano-biosorbents. These findings verify that members of the endophytic fungal genera Alternaria and Chaetomium are suitable to produce nano-biosorbents for decontamination practices after treatment by gamma mutagenesis, heat inactivation, and NSi immobilization. Moreover, statistical optimization can assist to evaluate the optimal conditions to produce such bioremediation material.

Nickel adsorption from waters onto Fe3O4/sugar beet pulp nanocomposite

In this study the magnetic nanocomposite material was synthesized with Fe3O4 impregnated to sugar beet pulp using chemical precipitation technique. Ni(II) removal performance of magnetic nanocomposite was investigated under different environmental conditions such as contact time, adsorbent dose, pH, initial heavy metal concentration, etc. The experimental studies have shown that, 81.2% Ni(II) removal efficiency was achieved at optimal conditions (25 mg/L initial Ni(II) concentration at 40 minute contact time, 200 rpm shaking speed, 5 g/L nanocomposite dose and pH 6.6). Freundlich and Langmuir isotherm experiments were performed and correlation coefficients were determined as 94.5% and 99.4%, respectively. The maximum adsorption capacity of material was achieved as 9.36 mg/g. These findings indicate that the adsorption that takes place is a monolayer process. The results of the pseudo-second order kinetic model (R2 = 0.9947) indicate the chemisorptions process is used for Ni(II) removal using the electrostatic interaction. Thermodynamic studies illustrated that Ni(II) adsorption onto nanocomposite are exothermic and causes a decrease in the entropy. The adsorption of Ni(II) ions is non-spontaneous except for at low temperature and low initial concentrations. Nanocomposite characterization was illuminated with XRD, FT-IR, BET, TGA, TEM, SEM/EDX analysis.

Biosorption of copper (II) from aqueous solutions by raw and chemically modified Thymus pannonicus in batch and fixed-bed systems

ABSTRACT In this study, the Cu(II) biosorption potential of the raw (RTP) and modified Thymus pannonicus (MTP) leaves was investigated in batch and continuous systems. FTIR, SEM, SEM-EDX and Zeta potential analyses were used for the characterisation of biomass. In the batch system, pH, amount of biosorbent, initial heavy metal concentration, contact time and temperature parameters were studied. According to the optimum pH and biosorbent amount determined in the batch system, the effect of the flow rate and column bed height on the biosorption was investigated by MTP in the continuous mode. Langmuir and Freundlich isotherm models were used to explain the biosorption mechanism, and it was seen that both biomasses conformed to the Langmuir isotherm. Pseudo-first-order and pseudo-second-order kinetic models were used in kinetic studies, and both RTP and MTP followed the pseudo-second-order kinetic model. While the equilibrium was established in 20 min in the removal of Cu(II) with RTP, this value increased to 30 min with MTP. The maximum monolayer biosorption capacity was determined as 46.21 mg/g for RTP and 82.70 mg/g for MTP. Column studies showed that the MTP was successful in removing Cu(II) from the solution in the continuous system.

Biosorption of heavy metals in automobile panel workshop effluent using Bacillus safensis LAU13

Heavy metals are natural constituents of the environment, but improper application for human activities has altered their geochemical compositions and biochemical balance. There is a need to remediate heavy metals released into natural resources through anthropogenic activities. This paper centers on remediation by biosorption as an effective technique for reduction in the concentration of Mn, Co, Cu, Fe, Zn, Hg, Se, Cr, Pb and Cd using Bacillus safensis LAU13.Wastewater samples were obtained from Gbade automobile panel workshop, Grammar School area, Ogbomoso, Nigeria. Initial concentrations of heavy metals in the effluent samples after digestion were determined through Atomic Absorption Spectrometery (AAS). The glucose enriched wastewater samples were autoclaved, the inoculums cultured and subjected to bio-treatment using 250, 500, 750 and1000 µL dosages of Bacillus safensis LAU 13 (Gen Bank accession number KJ461434), a Gram-positive, mesophilic, spore-forming, aerobic and chemo- heterotrophic bacterium. Optical density of inoculated samples was determined through spectrophotometer and the growth monitored for 48hrs. Residual pellets were subjected to Scanning Electron Microscopy (SEM). Results showed that 100% removal was achieved for Mn2+ and Co3+. Chromium was reduced to a very minimal concentration, Zn2+, Cu3+, Pb4+and Se4+ were above average in the irremediation. Fe2+and Cd2+were remediated below average but very low remediation of Hg2+ with less than one percent removal. Optical density increased significantly showing rapid growth of micro-organism irrespective of glucose supplement, and 250 µL inoculum dosage has the optimum performance. SEM micrographs indicate certain accumulated aggregates taken as remediated heavy metals. The study confirmed efficiency of biosorption technique as an alternative to the conventional treatment methods of huge cost, and high precipitates and slurry. B. safensis LAU13 is therefore recommended as a bio-remediating agent in treating automobile workshop effluents with high amount of manganese, cobalt, chromium, zinc, copper, lead and selenium.

Optimization of the raw materials of biochars for the adsorption of heavy metal ions from aqueous solution.

In this paper, the material types were preferentially selected for different kinds of heavy metals, the effect of calcination temperatures on metal adsorption was investigated, and the adsorption mechanism was explored and summarized. The results show that the pseudo-first-order kinetic was better to fit the adsorption of heavy metals. The biomass type and pyrolysis temperature had an effect on the rate at which heavy metals were absorbed. Based on their adsorbed capacity, 350 °C pyrolyzed corn stalk char, 550 °C pyrolyzed peanut shell char, 450 °C pyrolyzed peanut shell char, 450 °C pyrolyzed peanut shell char, and 500 °C pyrolyzed wheat stalk char were shown to be the best adsorbents for Cr2O72-, Cd2+, Cu2+, Zn2+ and Pb2+, respectively. The largest adsorption rate were in the order of Cr6+ (Cr2O72-, 0.5380 /min) > Pb2+ (0.2276 /min) > Cd2+ (0.1354 /min) > Cu2+ (0.1273 /min) > Zn2+ (0.1000 /min), which might be positively related to the ion radius. Meanwhile, the yield of biomass decreased from 43.9% to 29.0% with the increase of pyrolysis temperature from 350 °C to 550 °C. In addition, the specific surface area and functional groups of the biochar, as well as the ionic radius and initial concentration of heavy metals affect the adsorption rate.

Microwave-assisted preparation of carboxylic graphene oxide-chitosan composite for adsorption of uranium and heavy toxic metals in water samples

ABSTRACT In this study, the microwave-assisted novel composite of carboxylic graphene oxide-chitosan (COOH-GO-CTS) was prepared by using carboxylic functionalized graphene oxide (COOH-GO). The prepared composite was characterized by FTIR, SEM, XRD, XPS and Raman spectroscopy successfully. The composite was used as an adsorbent material for the removal of heavy metals such as uranium (U), lead (Pb), chromium (Cr), and cadmium (Cd). Batch adsorption was carried out to study the effects of pH of the medium, initial concentration of heavy metals, amount of adsorbent dosage, contact time, and temperature. The removal percentages for U, Pb, Cr, and Cd were observed to be 92.4, 94.6, 90.2, and 90.6% at 5, 5.5, 3, and 5 pH, respectively. Adsorption isotherms were performed for Langmuir and Freundlich adsorption, and it was observed that the Langmuir adsorption isotherm well fitted (R2 > 0.99) the present adsorption study. The maximum adsorption capacities of the composite for U, Pb, Cr, and Cd were found to be 64.93, 384.61, 68.49, and 49.50 mg g−1, respectively. The heavy metal adsorption kinetics were also performed, and it was observed that the pseudo-second order was well fitted (R2 > 0.99) the present study. Further, the themodynamic studies confirmed the adsorption of the heavy metals to be endothermic and spontaneous in nature.

Synthesis of bi-component ZrO2/Ag nanotube for heavy metal removal

This study was conducted to synthesize bi-component ZrO2/Ag nanotubes through anodization and photoreduction methods. The synthesized nanotubes were characterized and adsorption tests were carried out to evaluate its performance in removing heavy metal, lead (II). ZrO2 nanotubes were synthesized by anodizing zirconium foil in an electrolyte composed of glycerol, ammonium fluoride, formamide, and distilled water. The effect of anodizing time and the annealing process on the morphology of synthesized nanotubes were studied. Bi-component ZrO2/Ag nanotubes were prepared through photochemical reduction which silver precursor solution undergoes Ultraviolet (UV) irradiation in the presence of the active reducing agent. Larger pore diameter and longer length of synthesized nanotubes were formed at the longer anodizing time and the walls of nanotubes were smoother without annealing. The effect of the initial heavy metal concentration and contact time on the adsorption efficiency of synthesized nanotubes was evaluated using lead (II) as the heavy metal ions. Overall, the percentage removal of lead (II) increased with longer adsorption time and higher initial concentration of the lead (II) ions.

Engineered microwave biochar from sago bark waste for heavy metals adsorption

Microwave pyrolysis is an energy, time, and cost-saving process for conversion of biowaste from agricultural sector into biochar. Sago bark waste was microwave pyrolyzed at 400 °C to produce sago bark microwave biochar (M−B), which was then treated with NaOH and HCl to generate acid-base modified sago bark microwave biochar (M−Bab). FTIR analysis evidenced the changes in functional groups in M−B and M−Bab. SEM analysis found that microwave pyrolysis resulted in the formation of open structures and pores on the M−B and acid-base modification increased the porous structure in M−Bab. BET surface area increased from 29.547 m2/g of (M−B) to 119.040 m2/g of (M−Bab) after acid-base modification. M−Bab demonstrated higher removal at low initial heavy metal concentrations in batch experiments. Best model to illustrate Cr (III), Ni (II), and Pb (II) adsorption by M−Bab best represented by Freundlich isotherm, while Cu (II) adsorption by Temkin isotherms. Conversion of sago bark waste to M−Bab is a potential solution for both water pollution remediation and the issue of sago bark waste overabundance.

Modeling of copper removal from aqueous solutions by using carbon-based adsorbents derived from hazelnut and walnut shells by artificial neural network

The aim of this study is to model the removal of copper from an aqueous solution using Artificial Neural Network (ANN). Two different carbon-based materials (biochar) obtained by pyrolysis of hazelnut and walnut shells were used as adsorbents in a batch adsorption system. The surface area of biochars with a porous structure obtained from hazelnut and walnut shells were 124.347 m2/g and 256.931 m2/g, respectively. In adsorption experiments, initial copper concentration, adsorbent amount, temperature, pH, contact time and mixing speed were the adsorption parameters considered for the system and defined as inputs in the modeling studies. Experimental results for removing copper ions were found by changing pH 2.5-5, initial heavy metal concentration 15-45 ppm, adsorbent amount 1-3 g/L, mixing speed 200-600 rpm and temperature between 25-45oC. The % copper removal, which is tried to be maximized during the modeling phase, was selected as the model estimation parameter and defined as output to the system. ANN training was done with the Levenberg–Marquardt (LM) feed-forward algorithm and the data was categorised into 50% training, 25% validation and 25% testing. The maximum epoch value was determined as 8 iterations. Correlation coefficient (R2) values of the system were determined as 99% for education, validation and testing for the two different carbon-based adsorbents.

Competitive adsorption of Ni(II) and Cu(II) ions from aqueous solution by vermiculite-alginate composite: batch and fixed-bed column studies

The present study introduces vermiculite-Alginic composite (VMT-ALG) as a low-cost adsorbent for the uptake of Ni(II) and Cu(II). The fabricated composite was characterized by Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR) analysis. The different process parameters such as contact time, pH, initial heavy metal concentration, and temperature were optimized. According to the experimental data, the Freundlich adsorption model with the coefficient determination of 0.9945 and 0.9925 is the best isotherm model to describe the adsorption of Cu(II) and Ni(II) by VMT-ALG, respectively. Also, the equilibrium study confirmed the heterogeneous adsorption for Ni(II) and Cu(II). Kinetic studies indicate that intra-particle diffusion would be the significant rate-limiting step of the adsorption process. Thermodynamic studies indicated that the adsorption process was physisorption and endothermic. Research on fixed-bed column (20 cm length and 1.0 cm inner diameter) has been carried out under different volumetric flow rates (10 and 20 ml/min) and different initial concentrations of Cu(II) and Ni(II) (250, 500, and 750 mg/l). The results of column data were successfully explained using the Thomas and Yoon–Nelson models. Finally, continuous adsorption studies for Cu(II) and Ni(II) simultaneous uptake from aqueous solutions were conducted by VMT-ALG composite. The results indicated that the adsorption capacity of Cu(II) and Ni(II) both increased with an increase in the concentration of metal ions, and decreased with an increase in the flow rate.

Phytoremediation in Removing Selected Heavy Metals from Aqueous Solutions

Bioaccumulation of Ulothrix zonate was compared for cadmium, copper, nickel, and zinc removal at various concentrations and contact time. The results of the present investigation showed that the lowest amount of Cd, Cu, Ni and Zn was adsorbed when the initial heavy metal concentration was 10 ppm whereas Cd showed highest concentration at 20 ppm and Cu exhibited greatest removal at 30 ppm. The metals Ni and Zn exhibited highest removal at 40 ppm. The value of Freundlich model constant (1/n) for different metals ranged from 0.334 to 0.721 and the values of Langmuir separation factor values (RL) varied between 0.111 and 0.722 which indicated favorable bio-sorption by the biomass of the algae. The order of metals uptake was found to be Ni>Zn>Cu>Cd. The finding of the study showed that U. zonate has much potential as a biosorbent for the sorption of Cd, Cu, Ni and Zn and indicated that the metal uptake was concentration-independent for Cd and Zn whereas for Cu and Ni an increase in initial metal concentration resulted in higher metal uptake. This present study leads the way for the future studies on the use of algae as a cheap bio-adsorbent for heavy metals removal in Iraq which is suffering from huge inland waste water.

Biosorption of Copper(II) and Iron(II) using Spent Mushroom Compost as Biosorbent

The application of the biosorption process and agricultural waste to treat heavy metals has drawn much attention. This method seems to be a more economical, environmentally friendly, and simple way for removing heavy metals from effluents. The study was conducted to explore the efficiency of the biosorption process utilizing spent mushroom compost to remove copper (II) and iron (II) from synthetic wastewater. Biosorption studies at different operating parameters, such as biosorbent dosage (1.0 – 5.0 g), pH (pH 4 – 8), contact time (1 - 30 minutes), and initial heavy metal concentration (10 - 100 mg/L), were conducted in batch experiments. The highest performance for copper (II) and iron (II) biosorption was found at 5.0 g biosorbent dosage of spent mushroom compost, unadjusted pH 6, 10 minutes of contact time, and 10 mg/L of initial concentration. The study was well fitted to the Langmuir isotherm model (R2 > 0.95) for copper (II) and iron (II) biosorption, which are much greater compared to the Freundlich model. The study is also very well suited to the pseudo-second-order (R2 > 0.999) than the pseudo-first-order kinetic models. In conclusion, the spent mushroom compost has the potential to be an effective biosorbent for removing copper (II) and iron (II) from synthetic wastewater.

Oxygen-functionalized Typha angustifolia biochars derived from various pyrolysis temperatures: Physicochemical properties, heavy metal capture behaviors and mechanism

Biochars treated with acids always presented enhanced sorption capacities for heavy metals. Biochars pyrolyzed at various temperatures have different compositions and present different oxidation states for the acid treatment. To optimize the surface oxidation of biochars, an appropriate pyrolysis temperature of biomass is of great importance. In this work, raw biochars prepared from Typha angustifolia at 300, 400, 450, 500 and 600 °C were oxidized by HNO3. The function of HNO3 mainly focused on the surface oxidation of biochars rather than the creation of micropores in matrixes. Biochars pyrolyzed at the higher temperature were more difficult to be oxidized by the acid. The HNO3-activated biochars (NABCs) enriched Pb(II) and Cd(II) under various geochemical conditions including contact time, pH, ionic strengths, coexisting HA, initial heavy metal concentrations and temperatures. NABCs exhibited excellent sorption capacities (i.e., 232.6 mg/g for Pb(II), 88.9 mg/g for Cd(II) at pH 5.0 and 298 K) which were 6.9 and 5.5 times higher than these of untreated biochars. The maximum uptake capacities toward Pb(II) and Cd(II) showed an excellent linearity with the values of [OCO content × Surface area], demonstrating the essential role of the surface OCO species to coordinate heavy metals. NABCs could be well reused for six cycles through desorption using the acid pickling.

Adsorption Features of Loess Calcareous Nodules to Heavy-Metal Ions in Aqueous Solution

This paper explores the use of calcareous tuberculosis as an adsorbent and heavy-metal ions (Cu2+, Zn2+, Cd2+, and Pb2+) as adsorbates, and the influence of varying levels of particle size, adsorption time, pH, adsorbent dosage, and initial concentration of heavy metals is studied through an experiment of single heavy-metal adsorption. In addition, the impact of the temperature and other factors on the adsorption of heavy-metal ions by calcareous nodules is analyzed to identify the optimal conditions for the adsorption of heavy-metal ions by calcareous nodules. As shown by the research findings, the adsorption rates of Cu2+, Zn2+, and Pb2+ gradually declined with the increase in particle size, with no evident effect on Cd2+. In the meantime, with further increases in factors such as the adsorption time, adsorbent dosage, and temperature, the adsorption rates of Cu2+, Zn2+, Cd2+, and Pb2+ experienced gradual increases. The adsorption rates of Cu2+, Zn2+, and Cd2+ gradually declined with the increase in initial concentration of heavy-metal ions, whereas the adsorption rate of Pb2+ experience increased first and then declined. As the pH increased, the adsorption rate of Cd2+ experience increased first and then declined at a slow pace. The adsorption rates of Cu2+, Zn2+, and Pb2+ increased first and then decreased. The adsorption capacity of calcareous nodules toward the four heavy-metal ions was in the order of Pb2+ > Zn2+ > Cu2+ > Cd2+. When the particle size was set to 0.25 mm, the adsorption time was set to 120 min, and the dosage was set to 0.6 g, the calcareous nodules included Pb2+, Zn2+, and Cu2+. Moreover, Cd2+ was able to achieve stronger adsorption capacity, with the adsorption rate able to reach 83.33%, 77.78%, 73.81%, and 81.93% of its maximum level. Therefore, as the particle size of the heavy-metal ions decreased, the adsorption capacity generally became stronger. As the adsorption time increased, the temperature and the amount of adsorbent also increased. The optimal pH value for the adsorption of calcareous nodules toward Pb2+, Zn2+, Cu2+, and Cd2+ was found to be 7, 6, 5, and 8, respectively, and the optimal temperature was 50 °C. In summary, calcareous nodules are a natural, low-cost, and effective adsorbent.

Treatment of compost as a source of organic material for bacterial consortium in the removal of sulfate and heavy metal lead (Pb) from acid mine drainage

Acid mine drainage can pollute the environment because it is acidic and contains toxic heavy metals. The purpose of this research was the application of a bacterial consortium to remove sulfate and reduce heavy metal lead (Pb) in acid mine drainage. The application was done in the bioreactor for acid mine drainage treatment that was treated with compost. Observations were made every five days and included observation of total bacterial growth using the Standard Plate Count (SPC) method, determination of sulfate content by gravimetry, determination of pH by use of pH meter, and determination of the concentration of heavy metal Pb using the AAS method. As a result, it was obtained that the treatment of non-sterile compost in acid mine drainage was able to reduce the initial heavy metal concentration of Pb of 84% and reduce the sulfate content by 72%, along with increasing pH and an increase in total bacterial growth. Meanwhile, sterile compost treatment was only able to reduce the Pb content by 63% and sulfate by 54%. This result indicates that the addition of compost is more effective than the treatment of sterile compost.

Copper and Lead Ions Removal by Electrocoagulation: Process Performance and Implications for Energy Consumption

Electroplating wastewater contains high amount of heavy metals that can cause serious problems to humans and the environment. Therefore, it is necessary to remove heavy metals from electroplating wastewater. The aim of this research was to examine the electrocoagulation (EC) process for removing the copper (Cu) and lead (Pb) ions from wastewater using aluminum electrodes. It also analyzes the removal efficiency and energy requirement rate of the EC method for heavy metals removal from wastewater. Regarding this matter, the operational parameters of the EC process were varied, including time (20−40 min), current density (40−80 A/m2), pH (3−11), and initial concentration of heavy metals. The concentration of heavy metals ions was analyzed using the atomic absorption spectroscopy (AAS) method. The results showed that the concentration of lead and copper ions decreased with the increase in EC time. The current density was observed as a notable parameter. High current density has an effect on increasing energy consumption. On the other hand, the performance of the electrocoagulation process decreased at low pH. The higher initial concentration of heavy metals resulted in higher removal efficiency than the lower concentration. The removal efficiency of copper and lead ions was 89.88% and 98.76%, respectively, at 40 min with electrocoagulation treatment of 80 A/m2 current density and pH 9. At this condition, the specific amounts of dissolved electrodes were 0.2201 kg/m3, and the energy consumption was 21.6 kWh/m3. The kinetic study showed that the removal of the ions follows the first-order model.

Optimal Operating Conditions for Adsorption of Heavy Metals from an Aqueous Solution by an Agriculture Waste

The aim of this work is to detect the best operating conditions that effect on the removal of Cu2+, Zn2+, and Ni2+ ions from aqueous solution using date pits in the batch adsorption experiments. The results have shown that the Al-zahdi Iraqi date pits demonstrated more efficient at certain values of operating conditions of adsorbent doses of 0.12 g/ml of aqueous solution, adsorption time 72 h, pH solution 5.5 ±0.2, shaking speed 300 rpm, and smallest adsorbent particle size needed for removal of metals. At the same time the particle size of date pits has a little effect on the adsorption at low initial concentration of heavy metals. The adsorption of metals increases with increasing the initial of metal concentration while above the 85 ppm, the removal efficiency was decreased. The phenomenon of adsorption of heavy metals on to Al-Zahdi Iraqi Date pits is exothermic process. The maximum adsorption capacity according to the Langmuir equation was 0.21, 0.149, and 0.132 mmol/g for Cu2+, Zn2+, and Ni2+ respectively. The adsorption equilibrium was well described by the Freundlich model. The results of Freundlich constants indicated that the adsorption capacity and adsorption intensity of Copper is larger than the Zinc and Nickel. The intraparticle diffusion was involved is this process but it is not the controlling step. The results of this study may inspire to find the optimal operating conditions for adsorption and develop that with large-scale production to clean the polluted water with heavy metals.

Enhancement of electrokinetic remediation of lead and copper contaminated soil by combination of multiple modified electrolyte conditioning techniques

Electrokinetic soil remediation is often impeded by the aggregation of small particles, within soil, during the procedure. The soil porous network is subsequently clogged which results in immediate process termination. In order to overcome this limitation, the feasibility of electrokinetic remediation coupled simultaneously with two enhancing techniques was investigated: modified periodic polarity reversal and catholyte pH control. The objective is to keep the soil pores unclogged in order to remove Pb and Cu from soil. Citric acid was used as anolyte, and 1 DCV.cm-1 was applied through the processing cell. This strategy showed 9.0 times better remediation results than that of unenhanced electroremediation. It was mainly owed to: (i) The pH adjustment that kept the catholyte ideally acid, thus avoiding the formation of metal hydroxide precipitates that could clog the soil pores. (ii) An increase of electro osmotic flow due to the modified polarity reversal technique. Approximately 96% of Pb and Cu were removed from soil. Duplicate results were obtained on soil with 10-fold the initial heavy metals concentration. This combined configuration ensured an unclogged path within soil and enhanced electrokinetic mechanisms efficiency against pollutants remediation.